Known automatic machines for sewing leather articles usually feature a head, cantilevered on the front of the base structure and equipped with means for supporting the needle and related operating means.
The needle is moved toward an arm, which is situated below, that acts as a horizontal support, on which the leather articles to be sewn rest. The needle moves also in a direction parallel to the support arm.
The above mentioned machines are equipped also with transport means that move the two edges of leather articles to be sewn positioned one over the other, after each stitch.
A machine of this type is disclosed in the U.S. Pat. No. 4,848,252 by Applicant. This machine features a guide with two longitudinal flat surfaces, upwardly convergent, that form respective work tops, on which the leather articles to be sewn are moved.
Over the guide, there is provided a longitudinal shaft, with an arm keyed thereto and provided at its free extremity with an arc-like needle. The shaft oscillates so as to alternatively move the needle between a raised position and a lowered position, in order to pierce the edges of the leather articles. The needle operates in combination with a rotary hook with a thread.
The above mentioned machine sews edges of two leather articles, e.g. shoe uppers and toe caps.
However, this machine cannot be used for sewing together the bottom and the upper, in case the shoe is of open type and a strip is to be joined to the bottom.
FIG. 12 shows, as an example, a shoe with an upper sewn along its edge to a bottom.
It is to be noted that in this case the sewing is visible both along the edge of the upper and along the edge of the bottom, thus forming a kind of decorative motif.
At present, the sewing of the bottom to the upper is often hand-made, that requires a specialized staff thus increasing manpower cost and subsequently, the final cost of the product, and moreover, the productivity is reduced.
Another problem deriving from the hand-made sewing lies in the necessity of a camber that is made in front part of the shoe by previously shaping the front part of the upper like a dome.
Other known automatic machines, so-called "Rapid", can sew the bottom to the shoe upper.
However, the use of these machines requires former joining of the bottom and the upper by means of glue; moreover, the shoe must be mounted on a suitable last during sewing.
Obviously, this results in considerable working complexity and consequently, affects the cost of the product and the productivity.